Any tips on working with fast cure resin?

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CharlesHouse

Active Member
I bought a two gallon kit of fast cure resin, and it cures so quickly that working with it seems difficult. Not only is work time around 4 minutes, it also bubbled a lot. I have a vacuum chamber but, at a four minute cure time, the bubbles will be hard by the time I get it poured.
 

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OdiWan72

Master Member
RPF PREMIUM MEMBER
Mix each component thorrowly, pour them into separate cups and degas these. Mix together, not trying to stir too much/ fast. Pay attention to humidity

Markus
 

CharlesHouse

Active Member
Thank you for the comment. Individually, they don't seem to need degassing. It isn't until mixed that they produce bubbles.
 

Joy

Member
Sounds like they have some moisture contamination. I just came off a line of issues with this problem. Wither your mixing gear is contaminated with moisture or it has gotten into the parts.
 

cavx

Master Member
RPF PREMIUM MEMBER
Are you able to mix less cat with this product?

From time to time I will use a cheap nasty polyester casting resin and I found that by reducing the amount of cat, that I can extend the pot life out to 15min (temperature pending of course). This gives me time to degas under vacuum and pour bubble free. The only down side to this is time. It can take up to 48 hours to cure before you can de-mold and up to 7 days before it is no longer tacky. So you have to ask what it more important - bubble free or time?

If I want both, then I use a more expensive urethane product and can de-mold bubble free casts in 6 hours.
 

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Wellss01

Member
You cannot vary ratios with "fast cast" urethane resins. A way to get a bit more pot life is to refrigerate your bottles before you pour. Urethanes rely on heat to cure, chilling them slows down the reaction.

The bubbles can be caused by two main things,
one being over mixing, when you stir, try to not whip bubbles into the urethane.
The second is water contamination. Urethanes are hydroscopic, over time they absorb moisture from the air. To prevent this, use dry air blanket to purge your containers after each use.
Also make sure there is no water present on what you are casting into.
 

CharlesHouse

Active Member
Are you able to mix less cat with this product?

From time to time I will use a cheap nasty polyester casting resin and I found that by reducing the amount of cat, that I can extend the pot life out to 15min (temperature pending of course). This gives me time to degas under vacuum and pour bubble free. The only down side to this is time. It can take up to 48 hours to cure before you can de-mold and up to 7 days before it is no longer tacky. So you have to ask what it more important - bubble free or time?

If I want both, then I use a more expensive urethane product and can de-mold bubble free casts in 6 hours.
It's 50/50. I don't mind waiting longer, but assume that, if I did 60/40 or something, it would never cure.

The resin is new and has only been used once, so I doubt it is contaminated.
 

cavx

Master Member
RPF PREMIUM MEMBER
It's 50/50. I don't mind waiting longer, but assume that, if I did 60/40 or something, it would never cure.

The resin is new and has only been used once, so I doubt it is contaminated.
I bought a bulk pack of the stuff I use yesterday and saw they also had a 5 min pot-life product right beside it.

Reading your response and I think you need to change to a different product with a longer pot life. You should be able to find products with a 15min pot life from the same product line. You might have to ask for it though.
 

PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
Same advice from the last thread:

Moisture/humidity and heat are most likely the culprits in cases like these. I don't know if you're using Smooth-On products, but Onyx is notorious for me for doing this. To the point where it even emits steam, I've experienced.

Beyond looking out for that, shaking absolutely helps. That's why it's on the jugs to say "SHAKE WELL BEFORE USING". When I work with those materials, I take that to heart; shake vigorously for a few minutes and let settle for a couple hours before I start casting.

Those two tricks solved my problems. Another thing to take into account is amount of material. The more you use; the more vigorous the reaction. So it's always a good idea to go in small doses.
 

CharlesHouse

Active Member
I bought a bulk pack of the stuff I use yesterday and saw they also had a 5 min pot-life product right beside it.

Reading your response and I think you need to change to a different product with a longer pot life. You should be able to find products with a 15min pot life from the same product line. You might have to ask for it though.
I intend to. But currently, I have two gallons and $100 into what I have.

Same advice from the last thread:
My question is more about using it well in that short amount of time. Even if there weren't excess bubbles, there would be some, and 5 minutes is barely long enough to mix and pour much less degas.
 

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PoopaPapaPalps

Master Member
RPF PREMIUM MEMBER
Then go slow and little at a time. Instead of using, say, 100 ml to cast, cut down to 50 or 25 ml; layer it until it's at your desired thickness. I'd rather spend 25 minutes to get a good, clean cast then get a bubbly mess in 5.
 

AlO

New Member
Living in a tropical environment (Darwin, Australia), i do almost all my large urethane pouring from the fridge. It slows the cure time waaaay down and should down on moisture contamination. If i'm doing multiple copies i'll pour the next batch of both parts into jugs straight after i've poured the previous mould, that way i can demould and have a quick clean up and my next resin is cold and ready to go. You're other option is just keeping it in the fridge (best to have a small bar fridge in your workshop as it's also handy for knockoff beers!)

As for bubbles, now that it's cold and kicking slow pour slow and thin, that should get most out.
 

cavx

Master Member
RPF PREMIUM MEMBER
I intend to. But currently, I have two gallons and $100 into what I have.
My question is more about using it well in that short amount of time. Even if there weren't excess bubbles, there would be some, and 5 minutes is barely long enough to mix and pour much less degas.
I think the comment from PoopaPapaPalps below is the way to go for you. Providing you don't get a dust contamination between pours, you should not even see the layering. As for bubbles, either the high pour method, let it run off a stick (another way to do a high pour) or don't mix aggressively. I did a complete bubble free mix and pour using some of that cheap nasty poly by simply not lifting the mixing stick off the bottom of the can. I opened the can and let it stand so it was bubble free. Then I added the cat really slowly and moved the stick back and forth and never lifted it. The end result was bubble free in a part 5" tall. So it can be done. I agree that it is better if you can degas though.

Then go slow and little at a time. Instead of using, say, 100 ml to cast, cut down to 50 or 25 ml; layer it until it's at your desired thickness. I'd rather spend 25 minutes to get a good, clean cast then get a bubbly mess in 5.
Living in a tropical environment (Darwin, Australia), i do almost all my large urethane pouring from the fridge. It slows the cure time waaaay down and should down on moisture contamination. If i'm doing multiple copies i'll pour the next batch of both parts into jugs straight after i've poured the previous mould, that way i can demould and have a quick clean up and my next resin is cold and ready to go. You're other option is just keeping it in the fridge (best to have a small bar fridge in your workshop as it's also handy for knockoff beers!)

As for bubbles, now that it's cold and kicking slow pour slow and thin, that should get most out.
Ha, pure gold hearing from someone up the top end. I was living in Darwin 20 years ago and yep, a beer fridge is a MUST HAVE for that place. Do they still make the "Darwin Stubby"? I almost kind of miss the two climates - wet (and damn hot) season and the dry (still too warm for the southerners) season. funny thing is that once I moved to back to QLD, I'd be the one at the BBQ wearing a coat at anything below 25 degrees.

We have been sweating it out here in Brsvagas and today I had my product sitting in a iced water to drop its temp and extend the potlife. Air temp at 4:30 was 31 degrees C, so yeah not good when pot life drops from 15min to about 8 in that temp.
 

Duncanator

Sr Member
Since it's new resin and it appears there's not a water contamination issue, your best bets to reduce bubbles is to not over mix,and then use a pressure pot if you have access to one.
The pressure pot doesn't make the bubble go away, it crushes them down to tiny sizes till the resin hardens.
 

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CharlesHouse

Active Member
I think on top, as there was basically a hard foam on top, but I used it to fill a watch body, so I can't see the entirety of the resin.
 

edspaged2

Well-Known Member
Living in a tropical environment (Darwin, Australia), i do almost all my large urethane pouring from the fridge. It slows the cure time waaaay down and should down on moisture contamination. If i'm doing multiple copies i'll pour the next batch of both parts into jugs straight after i've poured the previous mould, that way i can demould and have a quick clean up and my next resin is cold and ready to go. You're other option is just keeping it in the fridge (best to have a small bar fridge in your workshop as it's also handy for knockoff beers!)

As for bubbles, now that it's cold and kicking slow pour slow and thin, that should get most out.
when i I was making molds and pouring resin back home in the NT only a few months ago, I had left a couple pots of silicone under my verandah. The heat absolutely killed the pot life. 3% ratio catalyst to silicone and it was setting almost solid within five minutes of mixing. My refrigerated stuff was still good. Same goes for my resin. I had two bottles of 50/50 out in the same area as my unrefrigerated silicone and part A went cloudy and a little bit yellow tinged and part B went even more yellow. They both still mixed together well although I noticed it did bubble a lot to the point of spilling out of the pour hole.
 

detenten

Active Member
This is a basic question, buy what do you guys use to stir your resin?

I've been using wooden popsicle sticks, though I know they're prone to absorbing moisture and are a potential source of the contamination that causes those bubbles that plague my castings...

I thought about those plastic coffee stir sticks, but I'm not sure they will allow to scrape the sides and mix well enough?
 

renaissance_man

Sr Member
RPF PREMIUM MEMBER
Make sure you mix your resin in a plastic cup and use plastic sticks to mix your resin, wooden sticks will still contain and also absorb atmospheric moisture which will effect the resin cure.
 

cavx

Master Member
RPF PREMIUM MEMBER
This is a basic question, buy what do you guys use to stir your resin?
Polyurethane - Mixed in a plastic Ice Cream container and stirred with wooden tongue depressor (the big popsicle sticks).
Polyester - Mixed in a plastic Ice Cream container and stirred with wooden tongue depressor. Whilst Polyester resin cure within a few hours, it seems to take up to 7 days to fully cure and not smell anymore.

I degas both prior to pouring.
 

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